1. Field of the Invention
The invention relates to a vehicle-mounted controller mounted on a vehicle having a high-voltage battery, vehicle-mounted information equipment, a low-voltage battery, and a voltage converter that performs voltage conversion between the high-voltage battery and the low-voltage battery.
2. Description of Related Art
Conventionally, a vehicle-mounted controller that uses a high-voltage electric power line as a communication line is available (see, e.g., Japanese Patent Application Publication No. 2012-110155 (JP 2012-110155 A)). The vehicle-mounted controller is mounted on a vehicle that includes a high-voltage battery, vehicle-mounted information equipment, a low-voltage battery, and a voltage converter. The high-voltage battery is charged by electric power supply from electric vehicle supply equipment (e.g., a charging station provided in a gas station or the like or a commercial power supply provided in a house) via a charging cable. In addition, the high-voltage battery supplies operation power to a motor that generates drive power. The vehicle-mounted information equipment performs communication, via the charging cable, with the electric vehicle supply equipment or an external information device connected to the electric vehicle supply equipment. The low-voltage battery supplies operation power to vehicle-mounted auxiliary machines including at least the vehicle-mounted information equipment. The voltage converter performs voltage conversion between the high-voltage battery and the low-voltage battery.
In the vehicle-mounted controller described above, when the voltage of the low-voltage battery becomes lower than a first threshold during the accessory-off state of the vehicle, the voltage converter is controlled such that the low-voltage battery is charged by electric power supply from the high-voltage battery. Thereafter, when the voltage of the low-voltage battery exceeds a second threshold, the operation Of the voltage converter is stopped such that the charging of the low-voltage battery is stopped. Consequently, when the vehicle-mounted information equipment performs communication with the equipment or device outside the vehicle during the accessory-off state of the vehicle, it is possible to prevent the exhaustion of the low-voltage battery that supplies electric power required for the communication to the vehicle-mounted information equipment.
However, in the controller described in JP 2012-110155 A, it is necessary to provide a voltage sensor for detecting the battery voltage of the low-voltage battery in order to prevent the exhaustion of the low-voltage battery when the vehicle-mounted information equipment performs communication with the equipment outside the vehicle, and hence there is a possibility that the controller is increased in size.